What's the Difference Between Cask and Keg Beer?

The main difference is that cask beer is naturally conditioned and carbonated in the cask, unfiltered and unpasteurised, and served at cellar temperature, resulting in a smoother, richer taste. In contrast, keg beer is filtered, pasteurised, and force-carbonated with CO2 or nitrogen, served colder, and has a crisper, more fizzy character. This makes cask beer a 'live' product with a shorter shelf life, while keg beer is more stable and consistent. 

Feature	Cask Beer	Keg Beer
Conditioning	Naturally carbonated by a secondary fermentation inside the cask.	Force-carbonated by injecting gas, typically carbon dioxide (CO2).
Filtration & Pasteurisation	Unfiltered and unpasteurised, with active yeast.	Filtered and often pasteurised to increase stability and shelf life.
Carbonation	Softer, more subtle carbonation from the natural fermentation.	Crisper, fizzier carbonation from the added gas.
Serving Temperature	Served at cellar temperature (around 11-13°C).	Served colder (around 3-7°C).
Flavour	Richer, more complex, and full of character.	Bright, refreshing, and often lighter on the palate.
Serving Method	Poured via a hand pump or gravity feed.	Poured through a tap using gas pressure.
Shelf Life	Lasts only a few days after being tapped, as it is a "living" product.	Can last for months due to filtration and pressurisation.